As of January 1, 2014, the Patient Protection and Affordable Care Act (ACA) requires all commercial, employer-based health plans, except for certain religious organizations, to cover contraception counseling and methods without patient copayments. Because about one-third of low-income women and 58% of all women are enrolled in such health plans in the United States, this provision could have broad implications for women's health. Many experts are optimistic that the ACA contraceptive mandate will reduce long-standing disparities in contraception use patterns and subsequently, unintended pregnancy rates. However, mandated full coverage of contraception-related services and methods has generated considerable controversy, and legal challenges are on-going placing this aspect of the ACA at risk of being partially or fully overturned. A clearer understanding of the clinical and economic impact of this policy on women, payors and the health system is needed to inform a balanced discussion. By using the natural experiment of the ACA's implementation to observe changes in patient cost-sharing, contraceptive method use patterns, pregnancies, and direct health care spending during the mandate's implementation, our proposed work will provide the data needed to assess the value of this policy. Our proposal is innovative in its framing around value-based insurance design (VBID) principles as a strategy to decrease unintended pregnancy. Under VBID principles, health plans should implement policies that encourage the delivery of evidence-based services. In this instance, the elimination of cost-sharing under the ACA for contraceptive-related services aligns patient financial incentives with clinical goals. We proposed to study the impact of the ACA among women within a large, national sample of women enrolled in employer-based insurance. This sample provides an ideal data source to characterize the impact of the ACA on contraception use, pregnancy/birth rates and expenditures broadly, and allows us to examine its impact across and within different income categories nested within health plans. Our work will provide the best available evidence on the ACA's impact on well-documented disparities in contraception use patterns, as well as clinical and economic outcomes by answering the following aims: 1) to determine whether the elimination of patient cost-sharing is associated with changes in contraception-related office visits, 2) to determine whether the elimination of patient cost-sharing is associated with changes in contraception non-use and contraception method fill patterns, including method type, consistency of use and method switching and 3) to examine whether the elimination of cost-sharing is associated with changes related to medical spending (i.e., spending from outpatient contraceptive-visits, pregnancy care, births and drugs). For each aim, we will examine the relationship between cost-sharing and our outcomes overall as well as across and within income categories.